10 Biogenic Reefs Flashcards
what are biogenic reefs?
- a habitat is a structure or setting e.g. rocky reefs, sedimentary bottoms…
(can be occupied by certain plants or animals) - marine habitats generated by the presence of organisms such as:
sea grass beds
kelp forests
oyster reefs
coral reefs
- including foundation species/ ecosystem engineers
What are foundation species/ ecosystem engineers?
- Species that generate whole habitats
- They often increase species diversity
- often facilitate the presence of numerous associated species by reducing environmental stress, and offering shelter and food
What are coral reefs?
Coral reefs are marine ridges or mounds, which have formed over millennia as a result of the deposition of calcium carbonate by
- living organisms, predominantly corals
- but also a rich diversity of other organisms such as coralline algae and shellfish
distribution of cold water and tropical coral reefs
What is Lophelia?
- a cold-water coral which grows in the deep waters throughout the North Atlantic ocean and can form extensive reefs
- example for coral of temperate mesotrophic coral reefs
mesotrophic habitats
- Oceanic waters with low light penetration (where less than 1% of light penetrates, approximately between 50 and 200 m depth)
- Corals, algae, and other organisms adapted to the low light conditions originate Marine Mesophotic Biogenic Habitats (MBHs)
the bathymetric zonation patterns incoral reefs are quite distinct. how?
- there is a transition from the light-dependent zooxanthellate corals to azooxanthellate scleractinian corals and sponges
- a transition from fleshy seaweeds to encrusting red algae
what are coralligenous reefs?
- unique hard bottom biogenic formations
- in the Mediterranean
- mainly produced by the accumulation of calcareous encrusting algae
- that grow in dim light conditions
distribution of coralligenous reefs in the mediterranean
coralligenous formations
- banks
- rims
what is a bank? (coralligenous formations)
- Banks are flat frameworks with a variable thickness that ranges from 0.5 to several (3–4) m
- mainly built over more or less horizontal substrata
- have a very cavernous structure that often leads to a typical morphology
what are rims? (coralligenous formations)
- Rims develop in the outer part of marine caves and on vertical cliffs
- usually in shallower waters than banks
- The thickness of rims is also variable and ranges from 20–25 cm to >2 m; thickness increases from shallow to deep waters
what is the dominant flora in coralligeneous reefs?
- main red algal building species
what is the dominant fauna
1) Fauna contributing to buildup from algae: bryozoans, polychaets, corals and sponges
2) Cryptofauna: colonizes small holes
3) Epifauna & Endofauna: living over or inside the buildup
4) eroding species
name some animal building species in coralligenous reefs
(A) Miniacina miniacea (B) Pentapora fascialis (C) Myriapora truncata (D) Serpula vermicularis (E) Leptopsammia
pruvoti
name some bioeroders incoralligenous reefs
A) Cliona viridis
(B) Sphaerechinus granularis
(C) Echinus melo
(D) browsing marks of Sphaerechinus granularis over Lithophyllum frondosum.
spatial interactions in coralligenous assemblages
- crucial in the buildup of coralligenous assemblages
are predators in coralligenous assemblages specialized?
- yes
- strong prey selection in coralligenous communities
Disturbances in coralligenous assemblages
what is the ecological role of marine animal forests?
- 3D habitat forming species
- nursery and refuge
- benthic-pelagic coupling
why are marine animal forests highly threatend?
(name disturbances)
- climate change
- pollution
- mechanical damages
- over-exploitation of resources
- non-indigenous species
what are maerl beds?
- maerl is a collective term of several species of calcified red seaweed
(e.g. Phymatolithon calcareum, Lithothamnion glaciale, Lithothamnion corallioides and Lithophyllum fasciculatum) - they live unattached on sediments
- can form extensive beds in favorable conditions (typically 30% cover or more)
- mostly in coarse clean sediments of gravels and clean sands or muddy mixed sediments
- Maerl beds have been recorded from a variety of depths, ranging from the lower shore to 30m depth
- maerl requires light to photosynthesize, depth is determined by water turbidity
what are Ecosystem Services Provided by Bivalve Shellfish?
- regulating
- provisioning
- supportive
- cultural